. The Canadian field-naturalist. Natural history; Sciences naturelles. Figure 2. Scanning electron micrograph of a female Cycithiini politu with marsupium. collected from the Saint John River during the summer of 2004. Symbols are: g = gnathopod. m = marsupium. pli= T' pleopod. n 21: 0. 29 May 4 Jun 10Jun 18Jun 1 Jul 17 Jul 31 Jul 17 Aug 27 Aug 10 Oct Date Figure 3. Male to female sex ratio of Cyatluira polita during the stud\ period in the Saint John Ri\er estuar>. Data were pooled from four stations, and sample size (n) is given in brackets above each column. On 10 October, most adult
. The Canadian field-naturalist. Natural history; Sciences naturelles. Figure 2. Scanning electron micrograph of a female Cycithiini politu with marsupium. collected from the Saint John River during the summer of 2004. Symbols are: g = gnathopod. m = marsupium. pli= T' pleopod. n 21: 0. 29 May 4 Jun 10Jun 18Jun 1 Jul 17 Jul 31 Jul 17 Aug 27 Aug 10 Oct Date Figure 3. Male to female sex ratio of Cyatluira polita during the stud\ period in the Saint John Ri\er estuar>. Data were pooled from four stations, and sample size (n) is given in brackets above each column. On 10 October, most adult isopods collected were male, resulting in a different scale, thus the sex ratio is given abo\ e the bar. P < ). Mean salinities at Bell Point ( ± ppt) and Westfield ( ± ppt) were similar (Fisher's 95% CI of , ), while Millidgeville ( ± ppt) and Summerville ( ± ppt) were comparable (Fisher's 95% CI of ). Sediment composition varied among the four study sites but all generally consisted of easily drained sub- strates (no anoxia; Mercer 2005). Bell Point had the highest gravel content of the four (), with little sand () and hardly any silt (). Westfield had the highest percentages of sand () and silt () and the least amount of gravel (). Mil- lidgeville contained more gravel () than sand () and very little silt (). Summerville was similar to Millidgeville with abundant gravel () and sand () and little silt (). The sex ratio of C. polita \aried during the studv period, from a male:female ratio of 2:1 in May, declin- ing to :1 in July, and increasing to 21:0 in October (Figure 3). In late spiing, numbers of males exceeded females and large juveniles (probably maturing fe- males) were present (Figure 4). From earlx June to the end of August, there w ere more females than males. Small, free-living juxeniles, 2 to 3 mm in length, were first observed on 31 Juh 2004
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